the nems zoo's are these little bacteria things that have a symbiotic relationship with the nem.... they harvest the light, (bright colors) the left over the nem feeds off...
makeing feeding less required.
water conditions... no enough light, young tanks. exc exc
will make the zoos die/ exspelled..... what ever they go away... and when the RTBA is with out its zooxanthellae its unable to get its own food source from the light..
feeding it meat at this point is needed for life,
if you get one that doesnt even eat (sticky) not the greatest spot you wanna be in,
the bottom line is that if they loose there color.. they have to be fed